1. Technical Field
This disclosure is directed to electronic circuits, and more particularly, to the testing of electronic circuits.
2. Description of the Related Art
For many electronic systems and devices, the manufacturing process concludes with one or more types of tests to ensure proper functionality and operation within specified limits. The types of testing that may be conducted are wide and varying, and may be suited to the particular system/device. One type of testing that may be conducted for integrated circuits is known as scan testing. In an integrated circuit, scan chains made up of a number of serially-coupled scan elements may be implemented. Each scan element may provide access to one or more internal nodes within the integrated circuit that are otherwise inaccessible. Test stimulus data may be shifted in through the scan chain and applied directly to nodes coupled to the scan elements. After applying the test stimulus data, one or more clock cycles may be applied to the circuitry under test in order to cause logical transitions. Test result data may then be captured by scan elements and shifted from the integrated circuit to external test equipment, where it may be analyzed to determine if any failures occurred.
In some cases, the testing described above may be conducted ‘at-speed’, i.e. with the clock signal cycled at an operational frequency. At-speed testing may be useful to determine whether the tested circuitry performs under operating conditions that are likely to be encountered by the integrated circuit when implemented in an electronic system.